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Early Season Disease and Nematode Management (Bob Kemerait):

Early Season Disease and Nematode Management (Bob Kemerait): For a few, planting cotton has
already begun. For most, it is imminent and rapidly approaching; planting cotton across the state of
Georgia will be in “full-swing” in only a matter of weeks.
Given that the vast majority of Georgia’s cotton crop is “still in the bag”; I want to reiterate some
critically important decisions that can ONLY be done before the seed-furrow is closed. Once the seed is
covered, there will be many more decisions to be made; however short of replanting, growers must live
with some early choices.
My niche in the world of cotton production is “disease and nematode management”. I think about these
things every day and every night. I dream about nematodes and diseases sometimes. “What’s wrong with
you?” my children often ask me. Below are points I ask you to consider as we enter the 2021 cotton
season, decisions that are made, one way or another, when the furrow closes.


1. Nematodes and variety selection. I know, there is “yield potential” and there is everything else.
But, for a moment, consider “everything else”. Think about the damage caused by nematodes in
Georgia’s cotton crop, damage from southern root-knot, reniform, sting, and Columbia lance
nematodes. From surveys, we know that a significant number of fields planted to cotton in
Georgia each year are infested with one or more of these types of nematodes. For many, if steps
are not taken to manage the nematodes, yield loss is likely to occur. For fields infested with rootknot nematodes, and now those infested with reniform nematodes, growers have the opportunity to
plant root-knot and reniform resistant varieties. Nematode resistant varieties do NOT need a
nematicide for protection in the 2021 season. Planting nematode-resistant varieties also helps to
reduce nematode populations heading into the 2022 season as well.
There are several things growers must remember when choosing an appropriate variety where
nematodes are a problem. First, you should know what type of nematode is present in order to
determine if a resistant variety is appropriate. Second, recognize that there are agronomic
differences among nematode-resistant varieties, and the BEST variety will combine nematoderesistance AND agronomic traits. Third, where nematode populations are low, or moderate,
protecting a favorite nematode-susceptible variety with an appropriate nematicide may be as
profitable as planting a resistant variety, even with the cost of the nematicide.

2. Disease and variety selection. Although bacterial blight has not been a significant problem for
most cotton growers over the past several years, the potential for outbreaks of this disease are
possible. There is one BEST management practice for protecting a cotton crop against loss to
bacterial blight and this is to plant a disease-resistant variety. Again, as bacterial blight has not
been a serious problem in recent years, most growers aren’t too worried about it. Still, given the
potential for disease outbreaks, coupled with the fact that there is almost nothing further to be
done once the furrow is closed, it is prudent to at least consider planting a variety that has bacterial
blight resistance.


3. Using nematicides. Plant-parasitic nematodes are a constant threat to cotton production in
Georgia. When planting varieties that are susceptible to nematodes (and ALL varieties are
susceptible to sting and Columbia lance nematodes), it is important to consider the judicious use
of a nematicide. The fumigant Telone II offers the best protection, followed by in-furrow products
such as Velum (remember Velum Total is soon to be a “thing of the past” and that an insecticide
for thrips control MUST be mixed with Velum) and AgLogic 15G. Seed-treatment nematicides
are very convenient to use; however they will not have the “power” of Telone II, AgLogic 15G, or
Velum to battle nematodes at higher populations. After the cotton emerges, typically between the
5th and 7th true leaf stages, growers have the potential to EXTEND the nematode protection from
earlier treatments with foliar applications of Vydate CLV or Return XL.
Fusarium wilt on cotton in Georgia results from the interaction of the Fusarium fungus and
damage to the cotton roots from nematodes. The only chance to protect a cotton crop from
Fusarium wilt occurs by protecting the plants from nematodes prior to furrow closure. In addition
to other nematicides already mentioned (especially Telone II), use of Propulse (fluopyram +
prothioconazole) has been moderately effective in the control of Fusarium wilt.


4. Protecting against seedling disease. While there are several pathogens that cause loss of seeds
and young cotton seedlings (to include Pythium and Fusarium) in Georgia, the most common “bad
guy” is Rhizoctonia solani. Commercial cottonseed comes pre-treated with several effective
fungicides that generally protect the seed and seedlings from disease and stand loss. If growers
want to invest in added protection, either for “insurance” or because of increased risk to disease,
additional seed treatments can be purchased and/or fungicides (typically azoxystrobin) can be
applied in-furrow, at planting. Again, once the furrow is closed, there are no further options to
protect from seedling diseases.


5. Selecting a planting date. Planting date plays a role in disease management in at least a couple of
ways. To minimize risk to stand-loss from seedling diseases, growers should wait to plant cotton
until soil temperatures at the 4 inch depth are consistently at 65°F and above. Warmer soils
promote rapid germination of the seed and rapid growth of the seedling. Growers should delay
planting if colder and wetter weather is imminent. Colder and wetter weather slows germination
and growth and greatly increases risk to diseases and stand losses.
While there is still much to learn about Cotton leafroll dwarf disease, it appears that fields where
this disease is most severe have often been later-planted. As a measure to reduce risk to Cotton
leafroll dwarf disease, growers should do their best to avoid planting later in the season than is
necessary.
Nematodes and diseases will always be a threat to our cotton crop in Georgia. Some of our best
management options can ONLY be made prior to covering the seed with soil. I encourage you to make
these decisions carefully; few things will be more frustrating than to look back 100 days into the 2021
season and realize that problems now could only have been fixed 100 days ago.